The present invention relates to a deaerator designed for use in oil circulating lubrication systems.
The deaerator of the invention has been specially developed for the oil circulating lubrication system of a paper machine, but it can also be used in other areas of process engineering and in large assemblies of equipment employing oil circulating lubrication systems.
In the oil circulating lubrication systems of paper machines, some air is always mixed with the oil. Air bubbles in the oil impair its lubricating properties and e.g. prevent high-speed operation of paper machines.
A prior-art attempt to eliminate the problems resulting form the presence of air bubbles in the oil is to increase the amount of oil in the system by using a larger oil tank. This is based on the expectation that, as the oil stays longer in the tank, the air bubbles will have enough time to rise to the surface and get out of the oil before it returns to the lubrication circulation.
There are also various flow guides used in oil tanks to keep the oil longer in the tank and to allow more effective separation of air bubbles. However, by monitoring the oil flow and taking samples of incoming and outgoing oil, it has been found that usually only about 20% of the oil is moving in the tank. In other words, most of the oil in a large tank remains stationary and the incoming oil flows almost directly through the tank back to circulation without undergoing any notable purification or separation of air in the tank. The same fact has also been discovered in investigations, in which it has been established that the incoming oil and the outgoing oil contain practically equal amounts of air and other impurities.
To eliminate the problems described above, an apparatus according to patent specification DE 1038847 has been used. However, the apparatus presented in this specification is very complex and requires several power means for operation, and in addition it suffers from the significant problem described above, in other words, air is not separated in the large tank in the desired manner but only part of the oil flows along the path built through the tank while most of the oil remains stationary in the tank.